Cost-effective frozen master mix modification of a commercial methicillin-resistant Staphylococcus aureus PCR assay

J Clin Microbiol. 2009 Jun;47(6):1888-91. doi: 10.1128/JCM.00506-09. Epub 2009 Apr 22.

Abstract

The expense inherent to molecular diagnostics may be an overriding concern for a variety of clinical laboratories in the development of PCR-based methicillin-resistant Staphylococcus aureus (MRSA) active surveillance programs. BD GeneOhm MRSA assay master mix was reconstituted, aliquoted into SmartCycler tubes in 25-microl volumes, and frozen at -70 degrees C. One hundred percent of archival nasal swab lysates yielded the expected PCR results when incubated in master mix frozen for 1, 2, 3, and 4 weeks. A 98.8% concordance of the final result was observed upon prospective PCR analysis of 320 clinical lysates utilizing freshly reconstituted master mix and 2-week-frozen master mix. Initial unresolved rates generated by frozen master mix and freshly reconstituted master mix differed by 1.6% (P = 0.16). Of 50 MRSA-positive lysates, the titers of 32 (64%) were determined to the same value upon initial tandem frozen master mix and freshly reconstituted master mix utilization; the titers of an additional 14 were determined to the same value upon repeat testing. Frozen master mix maintains potency for at least 4 weeks, facilitating detection of MRSA from nasal swab lysates, and may decrease the amount of unused reagent up to an average of 33%.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Carrier State / diagnosis*
  • Freezing
  • Humans
  • Mass Screening / economics
  • Mass Screening / methods*
  • Methicillin-Resistant Staphylococcus aureus / isolation & purification*
  • Molecular Diagnostic Techniques / economics
  • Molecular Diagnostic Techniques / methods*
  • Polymerase Chain Reaction / economics
  • Polymerase Chain Reaction / methods*
  • Reagent Kits, Diagnostic / economics*
  • Sensitivity and Specificity
  • Staphylococcal Infections / diagnosis*

Substances

  • Reagent Kits, Diagnostic